JP2002083434A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device correspondent to double wavelengths which can be miniaturized without using a synthetic prism. SOLUTION: In the optical pickup device 200 using a semiconductor laser element 50 having a first light emitting part 36 and a second light emitting part 40, the first light emitting part 36 is disposed in the position where an image height is not generated and the second light emitting part 40 is disposed in the position where the image height is generated. When the first light emitting part 36 is driven, the same focus driving current is supplied from a focus drive part 120, and when the second light emitting part 40 is driven, an offset value having a prescribed size is generated from a offset generating part 126. The pickup device 200 is driven in the direction of a focus in the state that an object lens 54b is inclined by making differ one focus driving current of the focus drive part 120.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DVD / CD compatible optical pickup device and the like having different read wavelengths.
The present invention relates to an optical pickup device capable of reading more than one type of recording medium, and more particularly to an optical pickup device using a semiconductor laser element constituted by a one-chip laser diode that emits two laser beams having different wavelengths.

[0002]

2. Description of the Related Art Conventionally, a DVD / CD compatible reproducing apparatus which shares an optical pickup of a CD reproducing apparatus and a DVD reproducing apparatus has been actively proposed, and a DVD / CD compatible reproducing apparatus using an optical pickup having one wavelength and two focal points has been proposed. 2
There is a form such as a DVD / CD compatible reproducing apparatus using an optical pickup having two wavelengths.

[0003] Comparing the structure of CD and DVD, DVD
Is about half the thickness of the protective layer of the CD (0.6).
mm), when reproducing both optical discs using a single-focus optical pickup, if the light beam is condensed so as to be optimal on the information recording surface of the DVD, the protective layer through which the light beam passes will be applied to the CD. Since the light beam is thicker than a DVD, aberrations such as spherical aberration occur in the light beam, and the light beam cannot be optimally focused on the information recording surface of the CD. CD and DVD
Then, since the size of the information pits formed for recording is different, in order to accurately read each information pit, a beam spot having the optimum size for each information pit is set to a CD or a CD. It must be formed on the information recording surface of a DVD.

The size of the beam spot is proportional to the ratio of the wavelength of the laser beam to the numerical aperture of an objective lens for focusing the laser beam on an information recording surface. That is,
Assuming that the wavelength of the laser beam is constant, the beam spot becomes smaller as the numerical aperture becomes larger. Therefore, when reproducing CDs and DVDs with a single-focus optical pickup, if the wavelength of the laser beam is fixed and the numerical aperture is adapted to the information pits of a DVD, for example, the information pits of the CD are The spot becomes too small, and the reproduced signal when reproducing the CD is distorted, so that accurate reading becomes difficult. Therefore, a bifocal optical pickup capable of irradiating two laser beams that focus on different positions on the same straight line and form a beam spot of an appropriate size corresponding to the size of each information pit is provided. The used DVD / CD compatible reproducing apparatus has become mainstream.

For example, in the optical pickup device shown in FIG. 16, a first light source 10 for CD and a second light source 15 for DVD are combined by a first beam splitter 13 which is a combining prism, and an objective lens and a diffraction element are used. This is a DVD / CD compatible playback device using a bifocal lens configured, and its configuration and operation will be briefly described.

In FIG. 1, a first light source 10 generates a laser beam (shown by a broken line) having a wavelength (780 nm) optimum for reading information from a CD according to a drive signal from a first drive circuit 11. This is irradiated to a first beam splitter 13 via a grating 12 for generating three beams. The first beam splitter 13 reflects the laser beam from the first light source 10 and guides the reflected light to the second beam splitter 14.

On the other hand, the second light source 15 arranged at 90 degrees with respect to the first light source 10 responds to a drive signal from the second drive circuit 16 at an optimum wavelength (65) for reading information from a DVD.
A laser beam (shown by a solid line) of 0 nm) is emitted to the first beam splitter 13 via the grating 17. The first beam splitter 13 includes a second light source 15
Beam splitter 1 that transmits the laser beam from
Lead to 4.

The second beam splitter 14 includes a laser beam supplied through the first beam splitter 13,
That is, the laser beam from the first light source 10 or the second light source 15 is guided to the bifocal lens 19 via the collimator lens 18. The bifocal lens 19 includes the second beam splitter 14
A laser beam condensed from the laser beam at one point is used as information reading light, which is applied to an information recording surface of an optical disk 21 that is driven to rotate by a spindle motor 20.

A laser beam (indicated by a broken line) from the first light source 10 is condensed by a bifocal lens 19 so that the information recording surface C of the optical disk 21 is focused. Further, a laser beam from the second light source 15 (shown by a solid line)
Is focused by the bifocal lens 19 so that the information recording surface D of the optical disc 21 is focused.

The reflected light generated by irradiating the optical disc 21 with the information reading light from the bifocal lens 19 passes through the bifocal lens 19 and the collimator lens 18, is reflected by the second beam splitter 14, and The light passes through a cylindrical lens 22 which is a point aberration generating element and irradiates a photodetector 23. The photodetector 23 generates an analog electric signal having a level corresponding to the amount of irradiated light, and supplies this signal to the information data reproducing circuit 24 and the disc discriminating circuit 25 as a read signal.

The information data reproducing circuit 24 generates a digital signal based on the obtained read signal, and further demodulates and corrects the digital signal to reproduce information data. The disc discriminating circuit 25 is based on the size of a beam spot formed when a laser beam is applied to the optical disc 21 as disclosed in Japanese Patent Application Laid-Open No. Hei 10-255274, for example.
Is supplied to the controller 26.
The controller 26 responds to the disk identification signal to
Driving control is performed so that one of the driving circuit 11 and the second driving circuit 16 is selectively driven.

The controller 26 has a disk discriminating circuit 2
When a disc type signal indicating a CD is obtained from No. 5,
Only the first drive circuit 11 is driven. Therefore, the first light source 1
The laser beam emitted from 0 is the grating 1
2, the optical disk 21 is irradiated through an optical system including a first beam splitter 13, a second beam splitter 14, a collimator lens 18 and a bifocal lens 19. Then, the reflected light (return light) reflected on the information recording surface of the optical disk 21 is transmitted to the bifocal lens 19 and the collimator lens 18.
, Is reflected by the second beam splitter 14, passes through the cylindrical lens 22, and irradiates the photodetector 23.

When a disc type signal indicating DVD is obtained from the disc discrimination circuit 25, only the second drive circuit 16 is driven. Therefore, the laser beam emitted from the second light source 15 is applied to the optical disc 21 via the optical system including the grating 17, the first beam splitter 13, the second beam splitter 14, the collimator lens 18 and the bifocal lens 19. . Then, the reflected light (return light) reflected on the information recording surface of the optical disc 21 passes through the bifocal lens 19 and the collimator lens 18, and
The light is reflected by the beam splitter 14, passes through the cylindrical lens 22, and is irradiated on the light detection device 23.

That is, a first light source 10 for generating a laser beam having a wavelength optimal for reading information from an optical disk 21 having a relatively low recording density such as a CD, and an optical disk 21 having a high recording density such as a DVD. Light source 1 for generating a laser beam having a wavelength optimal for reading information from a device
5 is provided, and the one corresponding to the type of the optical disc 21 to be reproduced is selectively selected.

As described above, a DVD / CD compatible reproducing apparatus which requires two light sources requires a combining prism as compared with an optical pickup apparatus having a single light source, thus increasing the cost and increasing the first light source. When the light 10 is emitted from one surface of the first beam splitter 13, the second light source 15 needs to emit light from the other surface perpendicular to the first light source 10. However, there is a problem that the size of the optical pickup device becomes large.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a two-wavelength compatible optical pickup device which can be reduced in size without using a combining prism. It is in.

[0017]

According to a first aspect of the present invention, there is provided a first light emitting source for emitting a first laser beam, and a first light emitting source disposed in close proximity to the first light emitting source. Is a light-emitting means in which a second light-emitting source that emits a second laser beam having a different wavelength is integrated, an objective lens shared for reading by the first or second laser beam, and the objective lens is moved at least in a focus direction. Focus driving means for driving; an optical system for guiding the first and second laser beams toward a recording medium and for guiding a reflected beam reflected by the recording medium toward light detection means;
An optical pickup device capable of reading information on recording media having different reading wavelengths, wherein the focus driving means is symmetrical with respect to a dynamic center of a support that supports a movable body to which the objective lens is fixed. And at least one pair of driving coils, each of which is provided with a driving current and generates a driving force in a focus direction by receiving the driving current, supplies driving currents of different magnitudes to the pair of focus driving coils. Accordingly, the objective lens is driven in the focus direction while being inclined with respect to the focus direction.

The invention described in claim 2 is the same as the invention described in claim 1.
In the optical pickup device described in the above, the first and second light emitting sources are arranged at a position where one has an image height with respect to the objective lens, and the other is arranged at a position without an image height with respect to the objective lens, The focus drive means supplies a different amount of focus drive current to the pair of focus drive coils when driving the one of the first and second light emitting sources, and the focus drive current when driving the other. A focus drive current of the same magnitude is supplied to the drive coil.

Further, the invention described in claim 3 is the first invention.
3. The optical pickup device according to claim 2, wherein the focus drive unit includes an offset addition unit that adds an offset current to a drive current generated based on a focus error signal, and the pair of focus drive coils is provided. In one of the embodiments, the drive current is always supplied as a focus drive current, and the other drive current to which an offset current is added by the offset adding means can be supplied as a focus drive current.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to an optical pickup device 200 for reproducing DVDs and CDs or CDRs having different reading wavelengths. still,
The recording medium to be reproduced is not limited to these, and the present invention is applicable to any optical pickup device 200 that reproduces a plurality of disks having different reading wavelengths.

FIG. 1 is a configuration diagram of a main part of an optical pickup device 200 according to an embodiment of the present invention. The configuration of the optical pickup device 200 will be described with reference to the drawings. The optical pickup device 200 includes a semiconductor laser element 50 that is a light emitting unit that emits two laser beams having different wavelengths, a grating lens 51 that generates a pair of sub-beams for generating a tracking error from the emitted laser beam,
A half mirror 52 that reflects the laser beam emitted from the semiconductor laser element 50 and guides the laser beam to the optical disc 55, and transmits the laser beam reflected from the information recording surface of the optical disc 55 and guides the laser beam toward the photodetector 60; Collimator lens 53 for converting a laser beam into parallel light
A bifocal lens 54 for converging laser beams having different wavelengths to focus on different positions on the same straight line to form a beam spot of an appropriate size; and a cylindrical lens 56 as an astigmatism generating element. , And a light detecting device 60 as light detecting means.

The light detecting device 60 generates an electric signal of a level corresponding to the amount of irradiated light, and supplies it to the error signal detecting section 127 and the disk discriminating circuit 128. The error signal detection unit 127 supplies the obtained focus error signal to the focus drive unit 120, which is a focus drive unit, and supplies the obtained tracking error signal to a tracking drive unit (not shown). The focus drive unit 120 controls the focus direction of the bifocal lens 54 based on the focus error signal supplied from the error signal detection unit 127. The disc discriminating circuit 128 determines the type of the optical disc 55 based on the size of a beam spot formed when the optical disc 55 is irradiated with a laser beam as disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 10-255274. Then, it is supplied to the CPU 130. The CPU 130 selectively drives one of the first light emitting unit 36 and the second light emitting unit 40 of the semiconductor laser element 50 via the drive circuit 129 in accordance with the disc discrimination signal.

The CPU 130 controls the offset value of the offset generator 126 based on the disc discrimination signal. The offset generation unit 126 supplies an offset value of “1” indicating no offset to the focus driving unit 120 based on a control signal from the CPU 130 that has determined that the optical disk 55 is a DVD by the disk determination circuit 128. Further, the offset generation unit 126 supplies a predetermined offset value to the focus drive unit 120 based on a control signal from the CPU 130 that has determined that the optical disk 55 is a CD by the disk determination circuit 128. Such an offset value is provided for adjusting the optical axis direction of the objective lens 54b when controlling the bifocal lens 54 in the focusing direction.
Set in the case of DR. Although the details will be described later, the bifocal lens 54 is driven by a focus drive coil 70 composed of a pair of left and right planar coils, and when the offset value is set, the focus drive current offset to one focus coil Is supplied to control the focus direction in a state where the optical axis of the objective lens 54b is inclined.

Next, the configuration and operation of each circuit block constituting the optical pickup device 200 according to the embodiment of the present invention will be described below. The photodetector 60 used in this embodiment is configured so that focus servo adjustment is performed by the astigmatism method and tracking servo adjustment is performed by the three-beam method. The configuration and operation of the light detection device 60 will be described with reference to FIGS. 2 is a diagram illustrating the configuration of the photodetector 60, FIG. 3 is a diagram illustrating the operation of the three-beam method, and FIG. 4 is a diagram illustrating the operation of the astigmatism method.

As shown in FIG. 2, the photodetecting device 60 divides the substrate 63 into four divided areas 1, 2, 3, and 4 for receiving the main beam M of the first and second laser beams. It comprises a unit 61 and two sub-detecting units 62a and 62b that receive the sub-beams S1 and S2 of the first and second laser beams used for generating the tracking error signal.

In the three-beam method, as shown in FIG. 3, two sub-beam spots S1 and S2 are divided into a main beam spot M
Are offset in the opposite direction by Q, respectively. The offset amount Q is set to about 1/4 of the track pitch P. The light reflected by each of the sub beam spots S1 and S2 is detected by the sub detectors 62a and 62b, respectively, and the difference between the detection outputs becomes a tracking error TE signal.

A four-division detection unit 61 for performing the astigmatism method
In the case where the beam spot has a perfect circular shape as shown in FIG. 4B, the areas of the beam spots irradiating the light receiving units which are diagonally opposite to each other are equal, and the focus error F
The E signal component becomes “0”. When the lens is out of focus, an elliptical beam spot is formed in the diagonal direction as shown in FIG. 4A or 4C due to the astigmatism characteristics of the cylindrical lens 56. In this case, the area of the beam spot irradiated on the light receiving portion on one diagonal line is different from the area of the other light receiving portion, and is output as a focus error FE signal. Then, an electric signal is supplied to the demodulation circuit and the error signal detection unit 127 according to the spot images formed on the four light receiving surfaces.

Next, the semiconductor laser device 50 constituting the optical pickup device 200 according to the embodiment of the present invention will be described. The semiconductor laser device 50 used in this embodiment has a first laser beam for reading DVDs and having a wavelength of 650 nm, and a first laser beam for reading CDs or CDRs having a wavelength of 780 nm.
m is a one-chip laser diode 30 that emits two wavelengths of a second laser beam, the structure of which is shown in FIGS.
It was shown to. FIG. 5 is a cross-sectional view of the one-chip laser diode 30, and FIG.
0 is a submount diagram.

The external dimensions of the one-chip laser diode 30 are 300 μm × 400 μm × 1 as shown in FIG.
An n-type AlXGaYIn 1-X-YP layer 33 and an AlxGaY
In1-X-YP active layer 34 and p-type AlXGaYI
An n1-X-YP layer 35 is laminated, and a first light-emitting portion 36 serving as a first light-emitting source for emitting a first laser beam having a wavelength of 650 nm is formed at the center of the active layer 34, and an n-type Al
An XGa1-XAs layer 37, an AlXGa1-XAs active layer 38, and a P-type AlXGa1-XAs layer 39 are stacked, and a second light source that emits a second laser beam having a wavelength of 780 nm at the center of the active layer 38 is used. Two light emitting portions 40 are formed, and the two active layers 34 and 38 each having a thickness of about 4 μm have a structure separated by a separation groove 32. Therefore, the first light emitting unit 36 and the second light emitting unit 40 have a structure in which the first light emitting unit 36 and the second light emitting unit 40 are separated by approximately 100 μm by the separation groove 32.

The one-chip laser diode 30
Means that the common electrode 41 is provided on the bottom side of the GaAs substrate 31,
An Au electrode 42 for the first light emitting unit 36 is provided on the top surface side of the light emitting source.
An Au electrode 43 for the second light emitting unit 40 is provided on the top surface side of the second light emitting source.
Are formed respectively. That is, the one-chip laser diode 30 is the semiconductor laser device 50 in which one electrode of the first and second light emitting sources is formed as a common electrode.

In general, a "one-chip" device means a device capable of outputting a laser beam of two wavelengths by forming two different types of active layers on a single chip by a selective growth method or the like. However, in the present invention, an element formed by arranging two laser elements that emit a laser beam of one wavelength in a hybrid manner, for example, on a silicon wafer, that is, two single-wavelength laser elements are integrated into a unit. Hybrid types are also included.

The one-chip laser diode 30
Is used in the form of a submount mounted on a silicon wafer 44 on which two Al electrodes 45 and 46 are formed as shown in FIG. In other words, the submount is
Al electrode 45 for light emitting section 36 and Al for second light emitting section 40
The one-chip laser diode 30 is placed on the silicon wafer 44 on which the electrodes 46 are formed, with the common electrode 41 facing up.
Are mounted, and the Au electrode 42 for the first light emitting unit 36 and the Au electrode 43 for the second light emitting unit are soldered to the two Al electrodes 45 and 46, respectively.
Lead wires (not shown) are soldered to the electrodes 45 and 46 for use.

When a predetermined voltage is applied between the common electrode 41 and the Al electrode 45, a wavelength of 650 n
m of the first laser beam is emitted, and the common electrode 41 and the Al
When a predetermined voltage is applied between the electrodes 46, a second laser beam having a wavelength of 780 nm is emitted from the light emitting window 48. First
Each of the beam shapes of the second laser beam and the second laser beam has an elliptical shape as shown in the drawing. The submount-shaped one-chip laser diode 30 is housed in a case provided with, for example, a light emitting window (not shown) and a plurality of output terminals,
Used as the semiconductor laser device 50.

As described above, the semiconductor laser element 50 includes the first light emitting section 36 for emitting the first laser beam having the wavelength of 650 nm and the second light emitting section 40 for emitting the second laser beam having the wavelength of 780 nm on the same chip. It is formed at a separated position. Therefore, as shown in FIG. 1, the optical path of the emitted light Ld of the first laser beam (dotted line in the figure) and the optical path of the emitted light Lc of the second laser beam (dashed line in the figure) do not coincide with each other and are slightly different.

Since the first laser beam and the second laser beam are selectively driven, two optical paths are not formed at the same time. However, for the sake of simplicity, the outgoing light L of the first and second laser beams is used in the drawings of this specification.
d, Lc, and incident light Ld of the first and second laser beams
f, Lcf and return light Lr of the first and second laser beams
Are described in the same drawing.

Next, the setting of the positional relationship between the first light emitting section 36 and the second light emitting section 40 will be described with reference to FIGS. Generally, in an optical system composed of a light source and an objective lens, the light source is used by being arranged on the central axis of the objective lens. However, the semiconductor laser device 50 of the present embodiment uses the first laser beam and the second laser beam as described above. Laser beam is approximately 100μ
Since the laser beams are emitted from a position separated by m, both laser beams cannot be arranged on the central axis of the lens. As shown in FIG. 7, it is known that when the light source Ei is arranged on the central axis Y of the lens L, the beam spot diameter becomes the smallest, and the beam spot diameter increases as the light source Ei moves away from the central axis Y of the lens L. . This is called coma aberration. When the center Ea of the light source does not coincide with the optical axis Y, the image height H is shifted, and coma aberration occurs. Since the coma has an adverse effect on the read signal, it is desirable to reduce it as much as possible.
It is necessary to optimize the positional relationship between the two light sources.

FIG. 8 shows the relationship between the image height and the aberration at the time of reproducing a CD or DVD, the dotted line shows the relationship between the image height and the aberration at the time of reproducing a DVD, and the solid line reproduces the CD. The relationship between the image height at the time and the aberration is shown.

As can be seen from the figure, the aberration at the time of reproducing the DVD is larger than the aberration at the time of reproducing the CD, regardless of the image height. Of aberration increase (inclination of solid line)
Larger than. Also, when the image height = 0, that is, when the light emitting point is arranged on the optical axis, the aberration at the time of reproducing the DVD is larger than the aberration at the time of reproducing the CD. this is,
This is because the numerical aperture of the objective lens is changed according to the wavelength of the laser beam used for reading. That is, D
VD is a laser beam having a wavelength of 650 nm and a numerical aperture of 0.6.
The CD is read by using an objective lens having a numerical aperture of 0.45. A lens having a larger numerical aperture makes it difficult to design a lens with reduced aberration. Therefore, the CD shown in FIG. The relationship is created. As a result, when a short-wavelength laser beam such as a DVD is read by an objective lens having a large numerical aperture, a CD is required.
As compared with the case where a long-wavelength laser beam is read by an objective lens having a small numerical aperture as described above, the laser beam is more likely to be adversely affected by the image height deviation.

Therefore, in the optical pickup device 200 of the present embodiment, the semiconductor laser element 50 is arranged such that the first light emitting section 36 for emitting the first laser beam for DVD reproduction, which is greatly affected by the aberration due to the image height deviation, is located at the center of the optical system. It is arranged on the axis, and is set at the optically best position with respect to the first laser beam. Accordingly, the second light emitting unit 40 that emits the second laser beam is disposed at a position away from the central axis of the optical system, so that the second laser beam is adversely affected by the image height deviation. As a method for solving the problem, by providing an offset generating unit 126 and supplying a predetermined offset value to the focus driving unit 120, the focus driving current of one of the focus driving coils 70 is changed, and the optical axis of the objective lens 54b is inclined. Thus, the image height deviation of the second laser beam is electrically corrected.

Next, the structure of the actuator 150 capable of correcting the image height deviation will be described with reference to FIG. FIG. 9 is an exploded perspective view of a main part of an actuator 150 constituting the optical pickup device 200 of the present embodiment, and FIG. 10 is a diagram showing a relative positional relationship between the printed coil substrate 150 and the magnet 153. In the figure, F indicates the focus direction, T indicates the tracking direction, and J indicates the jitter direction. The actuator 140 according to the present embodiment forms a movable body by fixing the objective lens 54 and the pair of printed coil boards 150 to the lens holder 100, and is capable of moving the movable body in the focusing direction and the tracking direction and moving the movable body in the focusing direction. It is supported to be tiltable. Specifically, four arm portions 101 formed on the lens holder 100 are provided on one end sides of four linear suspension members 116, 117, 118, 119 extending in the jitter direction.
The lens holders 100a, 101b, 101c, and 101d are coupled to each other, and the multi-end portion is coupled to an actuator base (not shown) to support the lens holder 100 in a floating state.

A pair of printed coil boards 150 are fixed to the lens holder 100 in a state of being arranged in the jitter direction. On each printed coil board 150, a pair of tracking coils whose coil surfaces are perpendicular to the jitter direction are provided. Coil 151a, 151b and focus coil 152
a, 152b are formed. On the other hand, a pair of magnets 153 constituting a magnetic circuit is provided on an actuator base (not shown), and a substantially U-shaped S pole surface 153 is provided.
a and an N pole surface surrounded on three sides by an S pole surface. These magnetic pole surfaces are surfaces perpendicular to the jitter direction, and include the tracking coils 151a, 151b and the focus coil 1.
52a and 152b face parallel to the coil surface.

As shown in FIG. 10, the tracking coils 151a and 151b are positioned so that their left and right halves face different magnetic pole faces, so that the tracking coils 151a and 151b have their left and right halves. Are provided with magnetic fluxes in opposite directions in the jitter direction. Also, the focus coils 152a, 152
b is positioned such that its upper half and lower half face different magnetic pole faces, thereby allowing the focus coil 152
The upper and lower halves a and 152b are provided with magnetic fluxes in opposite directions in the jitter direction.

Four linear suspension members 116-1
19, the linear suspension member 116 has a three-layer structure of a first metal linear portion 116a, an insulating material portion 116b, and a second metal linear portion 116c. The two-metal linear portion 116c is the insulating material portion 11
6b are electrically insulated. Similarly, the linear suspension member 117 has a three-layer structure including a first metal linear portion 117a, an insulating material portion 117b, and a second metal linear portion 117c, and includes a first metal linear portion 117a and a second metal linear portion 117c. The metal linear portion 117c is electrically insulated by the insulating material portion 117b. In addition, the linear suspension member 11
8 and 119 are entirely made of one layer of metal.

These linear suspension members 116 to
The reference numeral 119 also serves as a power supply line for driving current to the focus coils 152a and 152b and the tracking coils 151a and 151b. In the present embodiment, the pair of tracking coils 151a and 151b are connected in series by a connection line (not shown) so that the same tracking drive current is supplied. However, the focus coils 152a and 152b are A different focus drive current is supplied for the reason described later.
Then, the first metal linear portion 116a and the second metal linear portion 11
6c, first metal linear portion 117a, second metal linear portion 117
c, the linear suspension member 118 and the linear suspension member 119 are used as six input / output lines.

For example, the first metal linear portion 116a and the second
The metal linear portion 116c serves as an input line and an output line of a drive current for the focus coil 152a, and the first metal linear portion 1
17a and the second metal linear portion 117c carry an input line and an output line of the drive current to the focus coil 152b, and carry an input line and an output line of the drive current to the pair of tracking coils 151a and 151b. Can be. Next, a method of correcting an image height deviation according to the present invention will be described with reference to FIGS. FIG. 11 shows a focus coil 1 for emitting the first laser beam.
FIG. 12 is a diagram showing driving force vectors emitted from the reference coils 52a and 152b and their combined vectors. FIG. 12 shows a focus coil 152 for emitting a second laser beam.
It is a figure which shows the vector of the driving force emitted from a and 152b, and these combined vectors.

As described above, since the first light emitting section 36 for emitting the first laser beam is located on the central axis of the optical system,
The first laser beam does not cause an image height shift. Therefore, FIG.
As shown in FIG. 1, when emitting the first laser beam, the focus drive current i generated based on the focus error signal detected by the error signal detection unit 127
1, i2 are supplied to the focus coils 152a and 152b. That is, the focus coils 152a and 15a
2b is supplied with the same focus drive current. Then, the driving force F1 generated by the focus coil 152a and the driving force F2 generated by the focus coil 152b have the same magnitude along the focus direction, and the resultant force is
The force F acts on the mechanical center (and the center of gravity) G of the spring of the movable body. As a result, the objective lens 54b is driven in the focus direction based on the focus drive current without its optical axis tilting from the focus direction.
Although the mechanical center of the spring of the movable body and the center of gravity of the movable body do not always match, in an optical pickup that is the subject of the present invention, it is general that both are designed to substantially match each other. In the present embodiment, description will be made with an example in which they match. The dynamic center of the spring is the point at which the displacement of each suspension in the direction of the force due to the force applied to a plurality of suspensions is the same. In general, when a movable body is supported by four suspensions, If the cross-sectional shape and physical constants of the suspension are the same, a square centroid composed of four centroids of the cross-sectional shape of the suspension corresponds to this. In the present embodiment, four linear suspension members 116, 117, 118, 11
9 have the same cross-sectional shape and physical constants, and
7, 118 and 119 are the same, 116 and 118,
When the intervals between 117 and 119 are the same, a rectangular centroid composed of four centroids of the cross-sectional shape of each suspension is the mechanical center of the spring.

On the other hand, since the second light emitting section 40 that emits the second laser beam is located off the center axis of the optical system, the second laser beam causes an image height shift. Therefore, when emitting the second laser beam, one of the focus coils 152a and 152b is supplied with the focus drive current generated based on the focus error signal, while the other is provided with an offset current added to the focus drive current. The current is supplied. For example, as shown in FIG. 12, a current obtained by adding an offset current generated by the offset generating unit 126 to the focus driving current is supplied to the focus coil 152a.
b is supplied with a focus drive current. Then, the driving force F1 generated by the focus coil 152a is larger than the driving force F2 generated by the focus coil 152b, and the combined force is at a position separated from the dynamic center (and the center of gravity) G of the movable body spring in the tracking direction. The acting force F results. As a result, the movable body is driven in the focus direction while the drive point is always inclined by the difference of the drive force in the focus direction generated by the two focus coils, that is, the offset value, because the drive point deviates from the mechanical center of the spring. The Rukoto.

Next, the overall operation of the optical pickup device 200 according to the embodiment of the present invention will be described with reference to FIGS. FIG. 13 shows a case where a DVD is being played, and FIG. 14 shows a case where a CD or a CDR is being played.

As shown in FIG. 13, when the CPU 130 determines that the optical disc 55 to be reproduced is a DVD based on the disc discrimination signal from the disc discrimination unit 128, it controls the drive circuit 129 to operate the semiconductor laser element 50. The first light emitting section 36 is selectively driven, and an instruction is issued to the offset generating section 126 not to generate an offset current. Thereby, the focus driving unit 120
Generating a focus drive current corresponding to the magnitude of the focus error signal supplied from the error signal detection unit 127;
This is supplied to the focus coils 152a and 152b. That is, since the focus driving current of the same magnitude is always supplied to the focus coils 152a and 152b, as shown in FIG. 11, the focus driving force is the center of gravity of the dynamic center of the spring (and the movable body). Occurs at the position acting on

The emitted light Ld of the first laser beam emitted from the semiconductor laser element 50 is
The light is partially reflected by the half mirror 52 via the lens, is converted into a parallel light flux by the collimator lens 53, and then enters the bifocal lens 54.

The first laser beam incident on the bifocal lens 54 is diffracted by the diffractive element 54a into zero-order light, ± first-order light and other higher-order lights. The objective lens 54b focuses the zero-order light of the first laser beam on the information recording surface D of the optical disc 55.
Then, the return light Lr of the first laser beam reflected on the information recording surface D of the DVD passes through the bifocal lens 54 and the collimator lens 53, a part of which is transmitted by the half mirror 52, and passes through the cylindrical lens 56. Then, the main beam enters the first detection unit 61 of the light detection device 60, and the sub beam enters the two sub detection units 62a and 62b. The detection signal from the first detection unit 61 is used as a focus error FE signal, and the sub detection units 62a and 62
The detection signal from 2b is supplied to the error signal detection unit 127 as a tracking error TE signal.

On the other hand, as shown in FIG.
When the optical disc 55 to be reproduced is determined to be a CD or CDR based on the disc discrimination signal from the disc discrimination unit 128, the drive circuit 129 is controlled to selectively drive the second light emitting unit 40 of the semiconductor laser device 50. At the same time, it issues a command to the offset generating section to generate a predetermined offset current. The offset generation unit 126 calculates C
RO (not shown) based on a control signal from PU 130
The predetermined offset value stored in M, that is, the offset value “1.732” required to incline the optical axis of the objective lens 54b, for example, 15 degrees to the left, is set to the focus drive unit 12
Supply 0.

As a result, the focus driving section 120
A first focus drive current corresponding to the magnitude of the focus error signal supplied from the error signal detection unit 127 is generated, and further, an offset current generated by the offset generation unit 126 is added to the first focus drive current. A two-focus drive current is generated. And the first
The focus drive current is supplied to the focus coils 152a and 15a.
2b and the second focus drive current to the other. As a result, the focus coil 152
Since the focus driving currents having different magnitudes are always supplied to the a and 152b, the focus driving force is different from the dynamic center (and the center of gravity) of the movable body spring as shown in FIG. As described above, the objective lens can be driven in the focus direction in a state where the objective lens is tilted by the rotational moment, as described above.

The emitted light Lc of the second laser beam emitted from the semiconductor laser element 50 is
The light is partially reflected by the half mirror 52 via the lens, is converted into a parallel light flux by the collimator lens 53, and then enters the bifocal lens 54.

The first laser beam incident on the bifocal lens 54 is diffracted by the diffractive element 54a into zero-order light, first-order light, and other higher-order lights. Since one of them is used, the objective lens 54b focuses one of the primary lights of the incident light Lc of the second laser beam diffracted by the diffraction element 54a on the information recording surface C of the optical disk 55. At this time, the objective lens 54b is given a predetermined offset by the focus driving unit 120 and is controlled to be tilted in the focus direction, so that the beam spot of the second laser beam passing through the objective lens 54b is properly adjusted. It is formed on a pit on the information recording surface C in an aberration state.

Then, the return light Lr of the second laser beam reflected by the information recording surface C of the CD passes through the bifocal lens 54 and the collimator lens 53, and a part of the return light Lr is transmitted by the half mirror 52 to form a cylindrical lens. The light passes through 56 and enters the first detection unit 61 of the light detection device 60.
The detection signal from the first detection unit 61 is used as a focus error FE signal, and the detection signals from the sub detection units 62a and 62b are supplied to the error signal detection unit 127 as a tracking error TE signal.

As described above, in the optical pickup device 200 according to the embodiment of the present invention, the disc
When the disc discrimination result of step 8 is a CD or a CDR, an offset current is generated from the offset generation unit 126, and the focus drive unit 120 adjusts the magnitude of the focus error signal supplied from the error signal detection unit 127. A first focus drive current is generated, and a second focus drive current is further generated by adding the offset current generated by the offset generator 126 to the first focus drive current, and the first focus drive current is generated by the focus coil 152a. The second focus driving current is supplied to one of the first and second motors 152b.

Therefore, the second light emitting section 4 during CD reproduction
Since the image height deviation of 0 can be corrected by tilting the objective lens, the CD and CDR can also be suppressed from coma aberration and reproduced satisfactorily similarly to the DVD reproduction by the first light emitting unit 36 without the image height deviation. it can. Next, another embodiment of the present invention will be described with reference to FIG. As shown in FIG. 15, in the present embodiment, the power supply flex 200 is bridged between a movable body and a suspension base (not shown),
Thereby, the focus coil 152a or 152
b or the drive current is supplied to the tracking coils 151a and 151b. Therefore, the four linear suspension members 116 to
119 need not be an insulated multi-layer structure, but can be configured as a simple metal line. For example, the suspension members 116 and 119
The suspension members 117 and 119 serve as input and output lines of the drive current for the drive coil 2a.
2b, the input and output lines of the driving current for the driving current 2b.
It can be configured to serve as an input line and an output line of the drive current for the drive 51b.

In the optical pickup device 200 according to the present embodiment of the present invention, the first light emitting section 36 for emitting the first laser beam for DVD reproduction is arranged on the central axis of the optical system, and the second for CD reproduction is provided. The second light emitting unit 40 for emitting a laser beam is disposed at a position away from the central axis of the optical system, and
Although the offset is generated only at the time of reproduction, the present invention is not limited to this, and the offset may be generated at the time of DVD reproduction by arranging the second light emitting unit 40 on the central axis of the optical system. The first light emitting unit 36 and the second
The light-emitting unit 40 may be arranged at a position that is approximately the same distance from the central axis of the optical system, and an offset may be generated during both DVD playback and CD playback. In this case, D
The offset current at the time of VD reproduction and the offset current at the time of CD reproduction need to be set to different magnitudes.

Further, the optical pickup device 200 according to the present embodiment is configured as an infinite optical system by using the collimator lens 53 to convert divergent light into parallel light, but is not limited thereto, and may be configured as a finite optical system. . Further, when the optical pickup is designed with the mechanical center of the spring of the movable body different from the center of gravity of the movable body, the mechanical center of the spring should be designed to be the same as the focus drive point when there is no offset value. Is preferred.

[0061]

According to the present invention, the number of components of the optical system can be reduced, for example, the necessity of the combining prism can be eliminated, and the optical systems can be collectively arranged, so that the cost and space can be reduced. In addition, it is possible to reduce an error of a focus error signal caused by coma aberration, and to perform appropriate focus servo adjustment.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical pickup device according to an embodiment of the present invention.

FIG. 2 is a structural diagram of a light detection device used in the optical pickup device according to the embodiment of the present invention.

FIG. 3 is a diagram used for describing a three-beam method.

FIG. 4 is a diagram used for explaining an astigmatism method.

FIG. 5 is a structural view of a semiconductor laser device used in the optical pickup device according to the embodiment of the present invention.

FIG. 6 is a submount structure diagram of a semiconductor laser device.

FIG. 7 is a diagram showing a positional relationship between a light source and a central axis of a lens.

FIG. 8 is a diagram showing a relationship between image height and coma aberration.

FIG. 9 is an exploded perspective view of an actuator unit included in the optical pickup device according to the embodiment of the present invention.

FIG. 10 is a plan view of a printed coil included in the optical pickup device according to the embodiment of the present invention.

FIG. 11 is an explanatory diagram showing a method of correcting an image height deviation according to the present invention.

FIG. 12 is an explanatory diagram illustrating a method of correcting an image height deviation according to the present invention.

FIG. 13 is a view showing the operation of the optical pickup device according to the embodiment of the present invention.

FIG. 14 is a view showing the operation of the optical pickup device according to the embodiment of the present invention.

FIG. 15 is a perspective view showing another embodiment of the present invention.

FIG. 16 is a block diagram of an optical pickup device in a conventional example.

[Explanation of symbols]

 Reference Signs List 50 semiconductor laser element 51 grating lens 52 half mirror 53 collimator lens 54 bifocal lens 55 optical disk 56 cylindrical lens 60 photodetector 120 focus drive section 126 offset generation section 127 error signal detection section 128 disk discriminating circuit 129 drive section 130 CPU 200 optical pickup device

Claims (3)

[Claims] 1. A first light emitting source for emitting a first laser beam and a second light emitting source disposed in close proximity to the first light emitting source and emitting a second laser beam having a different wavelength from the first laser beam are integrated. A light emitting unit, an objective lens shared for reading by the first or second laser beam, a focus driving unit for driving the objective lens at least in a focus direction, and the first and second laser beams on a recording medium. An optical system that guides the reflected beam reflected by the recording medium toward the light detection means, and can read information on a recording medium having a different reading wavelength, Driving means are symmetrically disposed with respect to the mechanical center of a support that supports a movable body to which the objective lens is fixed, and each of the driving means receives a drive current and receives a focus. A pair of drive coils for generating the driving force of the direction of at least 1
A light source for driving the objective lens in a focus direction in a state where the objective lens is tilted with respect to a focus direction by supplying drive currents of different magnitudes to the pair of focus drive coils. Pickup device. 2. The focus driving means, wherein one of the first and second light emitting sources is arranged at a position having an image height with respect to the objective lens, and the other is arranged at a position having no image height with respect to the objective lens. Supplies a different amount of focus drive current to the pair of focus drive coils when driving the one of the first and second light emitting sources, and supplies the focus drive current to the pair of focus drive coils when driving the other. 2. The optical pickup device according to claim 1, wherein focus drive currents of the same magnitude are supplied. 3. The focus drive unit includes an offset adding unit that adds an offset current to a drive current generated based on a focus error signal, and the drive current is always focused on one of the pair of focus drive coils. While supplying as drive current,
3. The optical pickup device according to claim 1, wherein a drive current to which an offset current has been added by said offset adding means can be supplied as a focus drive current.